1. Field of the Invention
THIS INVENTION relates to tree harvesters.
The invention particularly relates, but is not limited to, tree harvesters suitable for harvesting shrubs, coppice or sapling trees, where such trees are planted at preferably regular spacings in rows.
2. Dictionary
The term “small trees” shall be used throughout the specification to describe shrubs and trees which have either a single-stemmed sapling form; or a plurality of coppice stems extending generally upwards from a tree stump or lignotuber; and by example, includes trees of the Eucalyptus and Acacia genera indigenous to Australia; and of the Salix and Populus genera indigenous to Europe and North America.
The term “in a substantially vertical position” will be used throughout the specification to indicate that a stem of a tree is inclined at an angle (preferably) no more than 30° to the vertical Z axis.
3. Prior Art
It has been proposed, in Australia, to grow trees of the Eucalyptus and Acacia genera as an ecologically-based answer to mankind's problems.
As the Eucalyptus and Acacia genera are fast-growing, their biomass can be used as a “renewable” source of energy, as the trees can be harvested every 2-6 years.
The second benefit of planting these trees is that some of the trees within the genera are salt tolerant and can be planted in areas, e.g., in Western Australia, where increased salinity levels have retarded the growing of other crops. The trees can also assist in lowering the water table, thereby reducing increases in the salinity levels near the soil surface.
Furthermore, they will take up CO2 gas from the atmosphere; and thereby assist the fight against global-warming.
The one disincentive to the proposal has been the ability to economically harvest the trees and transport the biomass from the tree growing areas to industry processors e.g., the electricity generating authorities, who will process the biomass to produce activated carbon or oil, and generate electricity.
It is not possible, with existing tree harvesters, to be able to achieve harvesting and transport costs that are economically viable.
In Europe, forage harvesters/maize harvesters/corn harvesters, e.g., of the types sold under the “Claas”, “Krone”, “New Holland” and “John Deere” Trade Marks have been modified to harvest certain trees. An example of such a “PRIOR ART” modified harvester will be hereinafter described with reference to FIGS. 1 to 3 of the accompanying drawings. These modified harvesters, however, have only been used to harvest European deciduous tree species, which generally have small-diameter, straight stems, and which are only harvested after they have dropped their leaves.